Zero Intermediate Frequency (ZIF) is a widely-used RF architecture in Wi-Fi technologies including most IEEE 802.11a/b/g/n/ac technologies and some IEEE 802.11ad technologies. A device using ZIF architecture transmits particular calibration signals, which are usually not frames or signals defined by 802.11 standards, over the air in order to perform RF circuit calibrations. The calibration procedure typically lasts for a certain predetermined time period. This is also sometimes referred to as the loopback mode.